Conventionally, silica fine particles with a hollow structure such as that shown in Patent Document 1 have been known as fine particles providing low reflectance (Low-n) and low dielectric (Low-k) constants. Recently, there is demand for greater void ratios in order to achieve greater performance. However, it is difficult to reduce the thickness of the outer shell in fine hollow silica particles, and the void ratio is likely to decline for structural reasons if the particle size is reduced to 100 nm or less.
Under these circumstances, because the void ratios of fine mesoporous silica particles are unlikely to decline for structural reasons as the particle size is reduced, they hold promise as next-generation high-void-ratio fine particles for application to low-reflectance (Low-n), low-dielectric constant (Low-k) materials and materials with low thermal conductivity. A molded article having these functions can also be obtained by dispersing fine mesoporous silica particles in a resin or other matrix-forming material (see Patent Documents 2 to 6).
In order to prepare a molded article having the superior functions of fine mesoporous silica particles, the high-void-ratio fine mesoporous silica particles must be supported in the molded article. However, in conventional fine mesoporous silica particles the void volume is too low, so that if the mesoporous silica content is low the functions described above cannot be obtained in a molded article, while if the mesoporous silica content is high the strength of the molded article is diminished. There have been attempts to increase the void ratios fine mesoporous silica particle. For example, in Non-patent Document 1 the mesopores are enlarged by the addition of styrene or the like, increasing the void ratio of the particles. However, in this method the shape and arrangement of the mesopores is irregular, and the strength of the molded article may be reduced for reasons having to do with the strength of the particles.    [Patent Document 1] Japanese Patent Application Laid-open No. 2001-233611    [Patent Document 2] Japanese Patent Application Laid-open No. 2009-040965    [Patent Document 3] Japanese Patent Application Laid-open No. 2009-040966    [Patent Document 4] Japanese Patent Application Laid-open No. 2009-040967    [Patent Document 5] Japanese Patent Application Laid-open No. 2004-083307    [Patent Document 6] Japanese Patent Application Laid-open No. 2007-161518    [Non-patent Document 1] Microporous and Mesoporous Materials 120 (2009) 447-453